Improvement of catalytic water oxidation on MnOₓ films by heat treatment

Zhou, Fengling, Izgorodin, Alex, Hocking, Rosalie K., Armel, Vanessa, Spiccia, Leone, and MacFarlane, Douglas R. (2013) Improvement of catalytic water oxidation on MnOₓ films by heat treatment. ChemSusChem, 6 (4). pp. 643-651.

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Manganese oxides (MnOₓ) are considered to be promising catalysts for water oxidation. Electrodeposited MnOₓ films from aqueous electrolytes have previously been shown to exhibit a lower catalytic action than films deposited from ionic liquids when tested in strongly alkaline conditions. In this study, we describe a thermal treatment that converts the MnOₓ films deposited from aqueous electrolytes to highly catalytic films with comparable activity to ionic-liquid-deposited films. The films deposited from aqueous electrolytes show a remarkable improvement in the catalysis of water oxidation after heat treatment at a low temperature (120°C) for 30min. The films were characterised by using XRD and SEM, and energy-dispersive X-ray (EDX), FTIR and Raman spectroscopy, which indicate that dehydration occurs during the heat treatment without significant change to the microstructure or bulk composition. The X-ray absorption spectroscopy (XAS) results show the growth of small amounts (ca. 3-10%) of reduced Mn species (Mn^II or Mn^III) after heat treatment. The dehydration process removes structural water and hydroxyl species to result in a conductivity improvement and a more active catalyst, thereby contributing to the enhancement in water oxidation performance.

Item ID: 28911
Item Type: Article (Research - C1)
ISSN: 1864-5631
Keywords: electrochemistry, manganese oxides, thin films, water splitting, x-ray absorption spectroscopy
Funders: Australian Research Council (ARC)
Date Deposited: 21 Aug 2013 09:22
FoR Codes: 03 CHEMICAL SCIENCES > 0302 Inorganic Chemistry > 030207 Transition Metal Chemistry @ 100%
SEO Codes: 85 ENERGY > 8504 Energy Transformation > 850402 Hydrogen-based Energy Systems (incl. Internal Hydrogen Combustion Engines) @ 50%
97 EXPANDING KNOWLEDGE > 970103 Expanding Knowledge in the Chemical Sciences @ 50%
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